A hypertension diagnostic screening clinic was established in the N.I.H. Outpatient department in December, 1974. Based on the results of several radiographic and biochemical tests, the type of hypertension evidenced by each patient is classified as accurately as possible. At the conclusion of the screening studies, patients may be included in further diagnostic or ongoing therapeutic protocol studies or an appropriate form of antihypertensive therapy is instituted. Since December 70 hypertensive and 25 normotensive subjects have participated in such a screening program. One patient with primary aldosteronism has been identified. 24% of the patients have suppressed plasma renin activity. No patients have died or have had either myocardial infarction or cerebrovascular accident since initiating this screening program.